The term “memory” subsumes many different processes and requires the function of many different brain areas. Overall, human memory provides declarative recall, e.g., for facts and events accessible to conscious recollection, and non-declarative recall, e.g., procedural memory of skills and operations not stored regarding time and place. Research in recent years has provided information necessary to understand many of the various components of memory and has identified associated brain regions. A newly acquired experience initially is susceptible to various forms of disruption. With time, however, the new experience becomes resistant to disruption. This observation has been interpreted to indicate that a labile, working, short-term memory is consolidated into a more stable, long-term memory.
Behavioral research has found that the human mind consolidates memory at certain key time intervals. The initial phase of memory consolidation occurs in the first few minutes after an exposure to a new idea or learning experience. The next phase occurs over a longer period of time, such as during sleep. If a learning experience has on-going meaning to us, the next week or so serves as a further period of memory consolidation. In effect, in this phase, the memory moves from short-term to long-term storage.
Moreover, various mechanisms have been proposed to account for the formation of long-term memory. A wide range of observations suggest an evolutionarily conserved molecular mechanism involved with the formation of long-term memory. These include increased release of synaptic transmitter, increased number of synaptic receptors, decreased KD of receptors, synthesis of new memory factors either in the presynaptic or postsynaptic element, sprouting of new synaptic connections, increase of the active area in the presynaptic membrane and many others. Synaptic plasticity, the change in the strength of neuronal connections in the brain, is thought to underlie long-term memory storage.
Memory consolidation, the process of storing new information in long-term memory is also believed to play a crucial role in a variety of neurological and mental disorders, including mental retardation, Alzheimer's disease and depression. Indeed, loss or impairment of long-term memory is a significant feature of such diseases, and no effective therapy for that effect has emerged. Short-term memory and working memory, are generally not significantly impaired in such patients.
Accordingly, methods and compositions that enhance long-term memory function and/or performance, or prophylactically (e.g., as a neuroprotective treatment) prevent or slow degradation of long-term memory function and/or performance would be desirable. Similarly, methods and compositions for restoring long-term memory function and/or performance are needed.
Impairments in cognitive and memory processes in a human can occur in a number of conditions or diseases, such as age-related memory loss, Mild Cognitive Impairment, Alzheimer's disease, Multiple Sclerosis, brain injury, brain aneurysm, stroke, schizophrenia, epilepsy, chronic fatigue syndrome, fibromyalgia syndrome, chemotherapy (e.g., cancer chemotherapy), traumatic brain injury, and Parkinson's disease. Following exposure to a muscarinic cholinergic receptor antagonist, such as atropine or scopolamine, humans can experience impairment of cognitive and memory processes. Clinical management strategies currently provide minimal, if any, improvement in memory and cognitive function. Thus, there is a need to develop new, improved and effective methods for the treatment of a human suffering with an impairment in cognitive and memory processes.